Haemodynamic studies in renal artery stenosis.

With the aid of an electromagnetic flowmeter and a mechano-electrical pressure transducer, peroperative renal artery blood flows and pressures in the aorta and the renal artery distal to the stenosis were measured in 48 patients with renovascular hypertension before and after renal artery reconstruction. Calculations of pressure difference across the stenosis and resistances over the stenosis and the renal parenchyma were made. There was a significant blood flow increase through the renal artery after arterial reconstruction in all patients, irrespective as to whether they were normotensive, improved or failures postoperatively. The pressure difference across the stenosis after reconstruction was eliminated in all 3 groups of patients. The highest resistances over both the stenosis and the renal parenchyma before arterial reconstruction were found in the normotensive group, but there was no significant variation between the 3 groups. After reconstruction, a significant decrease in resistance over the renal parenchyma was found in the normotensive and the improved group of patients. The resistance of the stenosis was higher than over the renal parenchyma only in the postoperatively normotensive patients. This indicates that the removal of a resistance over the renal artery stenosis, that is higher than that over the renal parenchyma, gives the most favourable long-term results concerning normalization of the blood pressure.